Cathode with graphite end shields

ABSTRACT

A tungsten dispenser cathode for a magnetron is described. The cathode is provided with end shields in the form of solid graphite rings to improve suppression of undesirable electron emission.

United States Patent {72] Inventor Johannes Antonius Van de Goor Emmasingel, Eindhoven, Netherlands [211 Appl. No. 770,668 [22] Filed Oct. 25, 1968 [45] Patented Jan. 12, 1971 {73] Assignee U. S. Philips Corporation New York, N.Y. a corporation of Delaware by mesne assignments [32] Priority Nov. 3, 1967 3 3 Netherlands [31 1 No. 6714947 [54] MAGNETRON CATHODE WlTl-l GRAPHITE END SHIELDS 3 Claims, 2 Drawing Figs.

[52] U.S.CI 313/107, 313/346, 313/356 51 no.0 ..1-10lj 19/06, 1101 j 19/42 501 Field ofSearch 313/107, 106,31l,345,346,355,356

Primary Examiner-R0y Lake Assistant ExaminerDavid OReilly Attorney-Frank R. Trifari ABSTRACT: A tungsten dispenser cathode for a magnetron is described. The cathode is provided with end shields in the form of solid graphite rings to improve suppression of undesirable electron emission.

PATENTEUJAWIQH 3555334 INVENTOR. JOHANNES A.VAN DE 600R 32% K AGENT MAGNETRON CATHODE WITH GRAPHITE END SHIELDS The invention relates to a magnetron in which the activated part of the cathode which consists of porous tungsten with alkaline earth metal compounds incorporated therein. is mounted or enclosed between rings the surface of which counteracts thermal emission.

ln known magnetrons the rings consist of carbonized or zirconium-coated molybdenum. Barium and/or barium oxide which migrates to said rings from the activated cathode part does not give rise to primary or secondary emissions thereon. The life of the known constructions, however, is not quite satisfactory because under the influence of the high operating temperature the molybdenum carbide decarbonizes and the zirconium difiuses into the molybdenum. The emission-inhibiting properties of the surface of the rings have then disappeared.

' It is an object of the invention to provide an improved construction.

According to the invention, in a magnetron in which the activated part of the electrode which consists of porous tungsten with alkaline earth metal compounds incorporated therein is enclosed or arranged between rings the surface of which counteracts thermal emission, said ring s rings consist of graphite.

Graphite has not only the property that also when coating the cathode with activating material the thennal emission is extremely low, but also due to the nonsmooth surface the secondary emission is very low. The graphite itself does not experience any change even after prolonged operation at the high cathode temperature.

The activated part of the cathode may be coated in known manner with osmium, iridium, ruthenium, rhenium or a similar material to increase the emission or to decrease the temperature. See US. Pat. Nos. 3,373,307 and 3,402,314 re for a more detailed description of the known tungsten dispenser cathodes with and without the emission-increasing coating.

in order that the invention may be readily carried into effect, two embodiments thereof will now be described in greater detail, by way of example, with reference to the accompanying drawing, in which:

FIG. I shows a cathode for a magnetron according to the invention of large continuous power; and

F IG. 2 shows a cathode for a magnetron according to the invention for producing pulses in the millimeter wavelength range.

Referring now to FIG. 1, reference numeral 1 denotes a molybdenum tube within which a heater element 2 is arranged. A porous tungsten cylinder 3 impregnated with barium calcium aluminate, the commercially available, so called Philips B" cathode, exactly fits around the tube 1. The cylinder 3 is rigidly enclosed or mounted between the rings 4 and 5 of graphite, which likewise readily fit the tube 1. The

graphite rings 4 and 5 are fixed by the welded narrow molybdenum rings 6 and 7. The diameter of the cylinder 3 is l4mm. The filament power of the element 2 is 200 Watt. A continuous power of 2 KW can be produced with a magnetron provided with the cathode as described above, at a frequency of 2450 mcls.

referring now to FIG. 2, reference numeral 8 denotes a profiled molybdenum body in which the heater element .9 is arranged in the thicker part. The aluminate-impregnated tungsten body 10 which exactly fits around the thinner part of the body 8, is enclosed or arranged between the graphite rings 11 and 12. A molybdenum ring 13 locks the ring 12. A plate 14 of molybdenum terminates the body 8 and supports one end of the heater element 9. The diameter of the body 10 is 2mm. The magnetron is suitable for a frequency of approximately 33Gc/s at which pulses of 2 5 KW peak value can be produced.

I claim:

1. In a magnetron-type electron tube having an electronand graphite rings are mounted ona common cylindrical support.

Tffgljff UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,555,334 Dated January 12, 1971 I fl JOHANNES ANTONIUS VAN DE GOOR It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 24, cancel "rings" (first occurrence) 7 line 34, cancel "re".

Column 2, line 18, "mcls." should read mc/s.

line 19, "referring" should read Referring Signed and sealed this 20th day of April 1971.

(SEAL) Attest:

EDWARD M. FLETCHERJR. WILLIAM E. SCHUYLER, JR Attestlng Officer Commissioner of Patents 

1. In a magnetron-type electron tube having an electron-emitting cathode comprising a porous tungsten cylinder with alkaline earth metal compounds incorporated therein and with emission-inhibiting rings mounted coaxially with adjacent opposite ends of the tungsten cylinder, the improvement comprising both of said rings consisting essentially of solid graphite.
 2. The magnetron of claim 1 and further including means for supporting said solid graphite rings in abutting relationship with the ends of the tungsten cylinder.
 3. The magnetron of claim 2 wherein the tungsten cylinder and graphite rings are mounted on a common cylindrical support. 